aka Ace Combat series, emulation, and you. Hints and tips to get Ace Combat games running on emulators.
Emulator used: any emulator of choice
- Most PSX emulator won't have issue running the three PSX titles anyway.
For Ace Combat 3, take a look at this 
Emulator used: PCSX2 v1.5.0 dev build (aka the latest you can get)
tl;dr Setup guide video by TugaAvenger 
tl;dw details for each individual games:
Ace Combat 04: Shattered Skies
- Player plane texture and explosion effect can't be fixed (yet) in GSDX HW mode, use SW mode
- Switch to SW mode (press F9) and go back to HW mode (press F9 again) during gameplay to fix the bugged sun effect
- Set CRC Hack level to "Minimum (Debug)" to fix flickering/disappearing HUD in missions: Lifeline, Operation Bunker Shot (AC04), and Emancipation
- Use OpenGL renderer to fix the hangar shadow covering almost entire screen
Ace Combat 5: The Unsung War
- When using DX11 renderer, highlighted menu buttons may appear completely blocked/blank, use OpenGL renderer instead
Ace Combat Zero: The Belkan War
- Enable "Alpha" GSDX HW Hack to fix the missing menu background (may apply to AC5 too).
Applies to all 3 games
- Using the latest PCSX2 dev build is a must. Old version has a fatal bug that makes 5 and Zero unplayable (missing hitbox for large planes and ground objects renders most missions unplayable without TLS/MPBM) and lacks of hardware mipmapping option that fixed the flickering ground texture.
- Enable mipmapping - basic option in graphics/GSDX config menu to fix flickering ground texture
- Using OpenGL instead of DX11 renderer allows more accurate graphic effects (i.e engine heat haze) at expense of FPS drop.
- Enable "Align Sprite" GSDX HW Hack to fix vertical black bars in HW mode
- Avoid using 3rd person view if the game runs too slowly, or set to lower internal resolution.
Emulator used: PPSSPP
Ace Combat X: Skies of Deception
- Should runs right off the bat without specific configuration. Using highest rendering resolution/texture scaling might slows down the game.
Ace Combat: Joint Assault
- ACJA requires specific emulator setting to avoid hang during FMV/prerendered cutscene playback. Go to Game Settings>System and set "I/O timing method" to "Host (bugs, less lag)". Having texture scaling enabled might introduces graphic artifacts on several planes. Haven't tried multiplayer so can't comment it yet.
Ace Combat 6: Fires of Liberation (Xbox 360)
Emulator used: Xenia
- Currently crashes after briefing, even if you're lucky you only can get as far as the loading screen (hint: constantly pressing F5 to refresh texture cache during briefing might let you get past the briefing screen) but then it crashes when you try to enter the game. Also the hangar screen doesn't display anything but the UI. Aside that, the intro FMV runs surprisingly smoothly while the first campaign FMV runs at less than 10 FPS. Also for some reason directional input doesn't work on keyboard control.
Ace Combat: Assault Horizon Legacy (3DS)
Emulator used: Citra bleeding edge
- Use the bleeding edge build, the vanilla build hangs before you enter a mission. AHL still runs slowly (20-sub 30 FPS) even on high spec PC but nevertheless perfectly playable from start to finish albeit the background music doesn't play (yet).
- More recent bleeding edge builds introduces rather severe HUD/particle glitches due to the removal of Geometry Shaders. Bleeding edge build 86 was the last version with Geometry Shaders so the bug didn't exist there however the emulation speed is significantly slower.
Ace Combat Advance (GBA)
Emulator used: any emulator of choice
- Self explanatory.
Ace Combat: Northern Wings (J2ME)
Emulator used: MicroEmulator
- For masochists, use J2ME emulator "Microemulator"  then drag & drop the .jar to the emulator. After that it's a matter of finding the jar with correct screen resolution (I found 176x208 to be the most compatible resolution)
Air Combat 22
Emulator used: MAME
- The latest MAME version should able to get it running (and Air Combat too but it's still too buggy to be playable so I don't bother with it) despite they still belong to NOT WORKING category - as they're still technically not fully playable yet expect tons of bugs. At least Air Combat 22 is playable until the end.
- Considering the game uses analog stick for control, aircraft handling may be quite a bitch since the flight physics doesn't allow barrel roll (aka NOVICE control only) that turning may be very twitchy. Either use a flightstick or mouse, personally I'm using mouse control with this configuration since I don't own flightstick/HOTAS 
- If during gameplay you find the aircraft throttle goes all over the place every time you increase/decrease throttle (P1 pedal 1 analog), set the P1 Pedal 1 settings in the "Analog Controls" menu according to my configuration above.